In an on-going collaboration with Drs. Angelo Russo and James B. Mitchell at the National Institute of Health, Nomadics has demonstrated the use of nanoparticles as fluorescence and spin contrast agents for optical and magnetic imaging simultaneously. In this project, we will develop functional imaging using near infrared (NIR) nanoparticles for oxygen measurement in tumors. Hypoxia is common in tumor and is one of, if not the, major determinant of cancer resistance to radiation therapy and chemotherapy. Likewise, the efficiency of Photodynamic Therapy is closely related to the concentration of oxygen in tumor. In addition, angiogenesis is closely correlated with oxygen distribution or gradients in tumor. Therefore, it is of great importance to interrogate tumor oxygen concentration and distribution. So far, the only commercially available sensor for oxygen detection is the polarographic needle electrode (Eppendorf(tm)) or Clark Electrode. The measurements of oxygen in tumor by Clark Electrode have provided valuable data to establish the relations between hypoxia and cancer treatment. However, there are still some obvious limitations when using Clark electrodes. Nanotechnology may offer new solutions to overcome the shortcomings of the present methods. In this project, we will demonstrate the potential for using NIR nanoparticles and oxygen intensity quenching and time-resolved decay lifetime techniques for oxygen detection. The combinations of these two techniques and the advantages of nanoparticle probes will enable the development a new oxygen sensor that can provide more accurate and more sensitive measurement of oxygen and oxygen-map imaging in vivo. [unreadable] [unreadable] [unreadable]